Hypoglycemia-induced cerebellar dysfunction and quantitative positron emission tomography study.

Abstract

OBJECTIVE: To describe an unusual case of hypoglycemia-induced bilateral cerebellar dysfunction. BACKGROUND: The cerebellum is known to be resistant to hypoglycemia, and selective cerebellar dysfunction caused by hypoglycemia has not been reported. Previous studies showed that the ratio between the rate constants for glucose uptake and phosphorylation (K1 and k3) is reversed in the cerebellum compared with the cerebral cortex; higher K1 in the cerebellum and higher k3 in the cerebral cortex. METHODS: Quantitative dynamic PET scanning with labeled fluorodeoxyglucose (18F-FDG) was performed to prove altered glucose kinetics in the cerebellum of a patient who presented with episodic cerebellar dysfunction associated with hypoglycemia. Four control subjects underwent the same study. RESULTS: The ratio between K1 and k3 was not reversed in the cerebellum of our patient (K1 = 0.082, k3 = 0.192). On the contrary, the ratio was reversed in the control subjects (mean K1 = 0.109, mean k3 = 0.080). In addition, the patient's cerebellar metabolic rate of glucose (rCMRglu = 27.9 micromol/100 g/minute) and the rate constant of glucose egress (k2 = 0.543) were relatively increased compared with those of control subjects (mean rCMRglu = 21.9 micromol/100 g/minute, mean k2 = 0.352). CONCLUSIONS: In a case of episodic bilateral cerebellar dysfunction caused by hypoglycemia, quantitative dynamic PET study demonstrated decreased glucose uptake-to-utilization ratio and increased leak of glucose in the cerebellum. The cerebellum is not invariably resistant to hypoglycemia.